Conventionally, a suction accumulator is an enclosed chamber, located between the evaporator and the compressor in a vapor-compression refrigeration system, used as a protective device for the compressor. However, quite often liquid refrigerant and oil is entrained in the return gas, and the presence of large enough quanties of such returning as slugs to the compressor could result in severe damage to this vital system component. Also, after such conditions as defrost or long-duration shutdown, condensed liquid refrigerant can often suddenly surge towards the compressor on startup. Such large volumes of liquid refrigerant or oil, if introduced into the compression chamber of positive displacement type compressors, due to its relative incompressibility, can result in so-called compressor slugging which can lead to severe damage to reeds or valves, pistons, and connecting rods. If the liquid is primarily condensed refrigerant, dilution of the lubricating oil can result, due to the high solubility of the oil in the liquid refrigerant, which can severely reduce the lubrication of the bearings and moving surfaces also cause compressor failure. Suction accumulators have been designed to prevent, or at least minimize, compressor failures such as these. Previous accumulator designs have provided for elaborate means of baffling, directing inlet gas/liquid flow away from the outlet gas flow stream in order to prevent the liquid entrapped in the gas stream from proceeding directly downstream to the compressor with the return gas, and the like. Such previous accumulator designs had an inherent low efficiency with respect to the pressure drop across the device. Since pressure drop across any component in the suction line of a refrigeration system has an adverse effect on the total system capacity and total pressure loss must be minimized.
An ideal accumulator should prevent slugging and at the same time should not cause burn-out by returning the oil to the compressor. In addition to these two functions, an ideal accumulator should offer as little resistance to flow, i.e., pressure drop, as possible and perform satisfactorily even at very low temperatures such as normally encountered in refrigeration systems of the type contemplated.
A solution to these basic problems has been devised and is shown in aforementioned U.S. Pat. No. 3,754,409 and is based on the idea of diverting the two phase flow entering the accumulator from the path of the flow leaving the accumulator. During this diversion, the liquid part falls below due to the action of gravity and the vapors, only vapors, leave the accumulator to enter the suction side of the compressor. As shown in U.S. Pat. No 3,754,409, this is accomplished by means of a J-tube of a certain configuration and arrangement and which also includes oil return and no flooding conditions by means of an orifice incorporated at the bottom of the J.
The present invention constitutes an improvement over the previous accumulators and that shown in the aforementioned patent, as well as the parent application.